Patent application title: METHOD FOR PRINTING ELECTRONIC DEVICE USING MATCHING LOGIC AND METHOD FOR MANUFACTURING RFID TAG USING THE SAME

Abstract:

A method of producing an electronic device by a roll-to-roll printing
process using matching logic, and a method of producing a RFID (radio
frequency identification) tag. The method, which enables mass production
of inexpensive printable electronic devices, includes: determining specs
of the electronic device; determining matching conditions including
substrate, ink and process conditions using impedance matching, chemical
matching, process matching, geometry matching, mechanical matching, and
time matching in view of the specs of the electronic device; printing
using a roll-to-roll printing process under the matching conditions;
examining a state of printed lines before and after drying; examining
conductivity of the printed lines after curing and checking any breakage
or short-circuit of the printed lines; testing final performance of the
electronic device; and repeating the steps of determining matching
conditions when any of the printed states, the conductivity, or the final
performance is not within respective predetermined error tolerance
ranges.

Claims:

1. A method of producing an electronic device by a roll-to-roll printing
process, using matching logic, the method comprising the steps of:(a)
determining specs of the electronic device;(b) determining matching
conditions for a roll-to-roll printing process using impedance matching,
chemical matching, process matching, geometry matching, mechanical
matching, and time matching while considering the specs of the electronic
device, the matching conditions including substrate conditions, ink
conditions, process conditions, and the type of a roll-to-roll printing
process of the electronic device;(c) printing an electric circuit on a
substrate by the roll-to-roll printing process under the matching
conditions;(d) examining a state of printed lines of the electric circuit
before the electric circuit is dried;(e) examining a state of printed
lines of the electric circuit after the electric circuit is dried;(f)
examining conductivity of the electric circuit after the electronic
circuit is cured;(g) testing final performance of the electronic device
in consideration of the specs of the electronic device; and(h) repeating
steps (b) and (c) if any of the states of printed lines in steps (d) and
(e), the conductivity in step (f), and the final performance in step (g)
is not within respective predetermined tolerance ranges of error.

2. The method of claim 1, wherein the ink conditions include the type of
ink, viscosity, a degree of mixing with a solvent, metal content and
metal particle size, and whether the ink is water-soluble or
lipid-soluble.

3. The method of claim 1, wherein the substrate conditions include the
type, width, thickness of a web material to be used as a substrate.

4. The method of claim 3, wherein the substrate conditions are determined
using the chemical matching in consideration of the surface tension and
roughness of the substrate, the degree of adhesion interaction between
the substrate and the ink, and drying and curing temperatures.

5. The method of claim 1, wherein the matching conditions determined using
the impedance matching include a thickness of a printed pattern and an
interval between neighboring lines in the printed pattern.

6. The method of claim 1, wherein the matching conditions determined using
the geometry matching include a depth, a width and an inner shape of a
cell in a printing roll, and a coating material of the printing roll.

7. The method of claim 1, wherein the matching conditions determined using
the process matching include a type of a roll-to-roll printing process of
the electronic device that is selected from the group consisting of
gravure printing, flexographic printing, ink-jet printing, offset
printing or hybrid printing.

8. The method of claim 1, wherein the process conditions include an
operation rate, an operation tension, a feed roll pressure, drying and
curing conditions, and are determined by using the mechanical matching.

9. The method of claim 8, wherein the drying conditions include the
duration, temperature and distance of a drying zone and means for drying,
and the curing conditions include the duration, temperature and distance
of a curing zone and means for curing.

10. The method of claim 8, wherein the process conditions further include
pressure of a riding roll for preventing inflow of air upon winding,
tension of each span between consecutive printing rolls, width-to-length
ration of the substrate, taper tension, precision of a register control,
and a cooling process.

11. The method of claim 1, wherein the matching conditions determined
using the time matching include change of a scheduling scheme and change
of register and tension control methods.

12. The method of claim 1, wherein examining a state of printed lines of
the electric circuit in (d) and (e) includes checking thickness,
thickness uniformity and any spreading of the printed lines.

13. The method of claim 1, wherein examining conductivity of the electric
circuit includes checking any breakage or short-circuit of the electric
circuit.

14. The method of claim 1, wherein the electronic device is selected from
the group consisting of a RFID tag, a solar cell, and signage.

15. A method of producing a RFID (radio frequency identification) tag by a
roll-to-roll printing process, using matching logic, the method
comprising the steps of:(a) determining desired values of a bandwidth and
a reading distance of a RFID tag;(b) designing a shape and a thickness of
an antenna adapted for the bandwidth and reading distance of the RFID
tag;(c) preparing ink for manufacturing the RFID tag;(d) determining
temperatures and distances, respectively, for a drying zone and a curing
zone, considering curing conditions of the ink and an anticipated
operation rate;(e) determining a substrate;(f) determining a type of a
roll-to-roll printing process, a cell shape and a cell depth;(g)
determining process conditions;(h) printing the antenna;(i) examining the
printed pattern of the antenna;(j) drying the substrate with the printed
antenna;(k) examining the printed pattern of the antenna;(l) curing the
substrate with the printed antenna;(m) examining conductivity of the
cured antenna;(n) bonding a RFID chip to the antenna;(o) testing final
performance of the RFID tag in view of the bandwidth and reading
distance; and(p) repeating steps (c) to (h) when any of the printed
pattern in steps (i) and(k), the conductivity in step (m), and the final
performance in step (o) is not within respective predetermined tolerance
ranges of error.

16. The method of claim 15, wherein designing a shape and a thickness of
an antenna in step (b) includes considering sensitivity of RFID driving
performance to work surroundings and noise under which the RFID tag is to
be used.

17. The method of claim 15, wherein preparing ink in step (c) includes
determining a type, viscosity, and metal contents of ink.

18. The method of claim 15, wherein determining a substrate in step (e)
includes determining the type, width, thickness of a web material to be
used as a substrate.

19. The method of claim 18, wherein determining a substrate in step (e)
further includes considering the surface tension and roughness of the
substrate, the degree of adhesion interaction between the substrate and
the ink, and drying and curing temperatures such that the substrate is
not melted at a drying temperature and a curing temperature.

20. The method of claim 15, wherein determining a type of a roll-to-roll
printing process in step (f) includes considering the type and viscosity
of ink and the type of substrate.

21. The method of claim 15, wherein determining a cell shape and a cell
depth in step (f) includes considering the shape and thickness of the
antenna.

22. The method of claim 15, wherein determining process conditions in step
(g) includes determining an operation rate, an operation tension, and a
feed roll pressure.

23. The method of claim 22, wherein determining process conditions in step
(g) further includes determining: pressure of a riding roll for
preventing inflow of air upon winding, tension of each span between
consecutive printing rolls, width-to-length ration of the substrate,
taper tension, precision of a register control, and a cooling process.

24. The method of claim 15, further comprising the step of determining
change of a scheduling scheme and change of register and tension control
methods.

25. The method of claim 15, wherein examining the printed pattern of the
antenna in steps (i) and (k) includes checking thickness, thickness
uniformity and any spreading of the printed pattern.

26. The method of claim 25, wherein examining the printed pattern of the
antenna in steps (i) and (k) includes visually checking the printed
pattern using a microscope.

27. The method of claim 15, wherein examining conductivity of the cured
antenna in step (m) includes checking any breakage or short-circuit of
the printed pattern.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims priority to and is a continuation of a
co-pending International Application No. PCT/KR2008/003727 filed on Aug.
4, 2008, which claimed priority to a patent application No. KR
10-2008-0043085, filed on May 8, 2008, in Korea, and hereby claims the
benefit thereof.

BACKGROUND OF THE INVENTION

[0002]The present invention relates to a method of printing electronic
devices in a roll-to-roll process, using a matching logic, for mass
production and reduction in production cost, and to a method of
manufacturing a RFID (radio frequency identification) tag.

[0003]A continuous roll-to-roll printing process has been long known and
used for printing conventional materials. Recently, it is receiving newer
and greater attention in the art for its potential applicability in
producing electronic devices because once implemented, it entails huge
advantages, including the capability of mass-producing inexpensive
electronic devices at reduced cost and time. As compared to this, the
conventional batch-type production of electronic devices is
disadvantageous because the production process is discontinuous and
complicated due to the use of etching, resulting in low productivity and
high production cost.

[0004]By contrast, a roll-to-roil process continuously produces a subject
matter and directly prints the subject matter with ink containing metal
nano-particles such as silver or nickel, therefore drastically increasing
production rate. In order to apply a conventional printing technique used
in a general printing medium to a roll-to-roll printing of an electronic
device, however, there is a problem to be solved, that the printing
precision must be greatly increased. The precision of a conventional
printing process is about one hundred microns, which indicates a minimal
error distinguishable with naked human eyes. However, many electronic
devices require a printing precision of one to fifty microns, or less in
some cases, depending on the field of application of the electronic
devices.

[0005]Therefore, in order to achieve such a high printing precision in
printing an electronic device using a roll-to-roll process, it is
critically important to accurately determine and control various product
parameters, and process conditions and parameters. More specifically, the
conditions and parameters that are important to printing an electronic
device by a roll-to-roll process, and therefore must be properly
determined include: ink conditions such as ink viscosity, degree of
mixing ink with solvent, the metal contents and metal particle size,
water or lipid solubility; substrate conditions such as the type, width,
and thickness of the substrate, the type of surface treatment needed,
surface tension, surface roughness, light transmittance; process
parameters such as substrate operation tension, operation rate, nip
force; cell shapes, cell depth, cell width; drying conditions such as
duration, temperature, distance, and means of drying; curing conditions
such as duration, temperature, distance, and means of curing; and the
type of a roll-to-roll process itself.

[0006]It has been known that many of these critical parameters and
conditions are mutually and delicately dependent on one another and that
the freedom of choice in determining the parameters and conditions is
limited not only by the targeted specs and functionality of the
electronic device to be produced, but also by physical or chemical
compatibility among different parameters and conditions. Changing one
parameter or condition may critically affect the choice of other
parameters and conditions as well as overall productivity and performance
of the electronic device. Therefore, to ensure the desired printing
precision and enhance the productivity, it is important for these
conditions and parameters to be determined in such a way to be adapted
for the targeted spec of the electronic device, and at the same time, to
match with one another physically, mechanically and chemically.

[0007]Although methods and techniques for printing electronic devices
using a roll-to-roll process have been studied in the art for its
potential huge benefits, up to date, there has not been developed any
systematic, comprehensive, and integrated methodology to determine and
control such various product and process parameters and conditions in
producing an electrical device such as a RFID tag using a roll-to-roll
printing process.

[0008]Therefore, there is a need in the art to devise a method of
producing an electronic device using a roll-to-roll printing process that
uses a logic, by which all critical product and process parameters and
conditions are determined, controlled, and recalibrated in a single
systematic, sequential, and integrated way so that the electronic device
may be produced in a large scale by a smooth, fast and continuous
roll-to-roll printing process with enhanced precision and lowered cost.

SUMMARY OF THE INVENTION

[0009]In view of the afore-described needs in the art, one object of the
present invention is to provide a method of producing electronic devices,
such as a RFID (radio frequency identification) tag, solar cells, or
signage, using a roll-to-roll printing process, which provides the
capability of mass production and significant reduction of production
cost and time.

[0010]Another object of the present invention is to provide a method for
producing electronic devices, in which all major conditions and
parameters critical to the roll-to-roll printing process are
systematically, sequentially, comprehensively, and interactively
determined and designed by an integrated logic such that they not only
match the desired specs of the electronic device, but also match
mutually.

[0011]Still another object of the present invention is to provide a method
of producing an electronic device using a roll-to-roll printing process,
in which the printing errors are repeatedly checked in production steps
where the errors are frequently caused, and can be eliminated by
conveniently and systematically recalibrating the conditions and
parameters of the roll-to-roll printing process by devising a logic.

[0012]In order to accomplish the above objects, an aspect of the present
invention provides a method of producing an electronic device by a
roll-to-roll printing process, using matching logic, which includes:
determining specs of the electronic device; determining matching
conditions for a roll-to-roll printing process using impedance matching,
chemical matching, process matching, geometry matching, mechanical
matching, and time matching while considering the specs of the electronic
device, the matching conditions including substrate, ink, process
conditions, and the type of a roll-to-roll printing process of the
electronic device; printing an electric circuit on a substrate using the
roll-to-roll printing process under the matching conditions; examining a
state of printed lines of the electric circuit before the electric
circuit is dried; examining a state of printed lines of the electric
circuit after the electric circuit is dried; examining conductivity of
the electric circuit after the electronic circuit is cured; testing final
performance of the electronic device in consideration of the specs of the
electronic device; and repeating the steps of determining matching
conditions and printing an electric circuit if any of the states of
printed lines, the conductivity, and the final performance in is not
within respective predetermined tolerance ranges of error.

[0013]The ink conditions may include the type of ink, viscosity, a degree
of mixing with a solvent, metal content and metal particle size, and
whether the ink is water-soluble or lipid-soluble, and the substrate
conditions include the type, width, thickness of a web material to be
used as a substrate, which are determined using the chemical matching in
consideration of, in one aspect of the present invention, the surface
tension and roughness of the substrate, the degree of adhesion
interaction between the substrate and the ink, and drying and curing
temperatures.

[0014]The impedance matching determines, in an aspect of the present
invention, a thickness of a printed pattern and an interval between
neighboring lines in the printed pattern, and the geometry matching
determines a depth, a width and an inner shape of a recessed cell in a
printing roll, and a coating material of the printing roll.

[0015]The process matching determines a type of a roll-to-roll printing
process of the electronic device, which is selected from processes that
may include, but is not limited to, gravure printing, flexographic
printing, ink-jet printing, offset printing or hybrid printing. The
mechanical matching determines, in an aspect of the present invention, an
operation rate, an operation tension, a feed roll pressure, drying and
curing conditions. The drying and curing conditions include the duration,
temperature distance of drying and curing zones, and means for drying and
curing.

[0016]In another aspect of the present invention, the mechanical matching
may further determine the process conditions such as pressure of a riding
roll for preventing inflow of air upon winding, tension of each span
between consecutive printing rolls, width-to-length ration of the
electronic device, taper tension, precision of a register control, and a
cooling process.

[0017]Time matching determines, in an aspect of the present invention,
change of a scheduling scheme and change of register and tension control
methods.

[0018]In an aspect of the present invention, when examining a state of
printed lines of the electric circuit, the thickness, thickness
uniformity and any spreading of the printed lines are checked visually,
and when examining conductivity of the electric circuit, any breakage or
short-circuit of the electric circuit is checked.

[0019]Another aspect of the present invention provides a method of
manufacturing an RFID tag using a matching logic, which includes:
determining desired values of a bandwidth and a reading distance of a
RFID tag; designing a shape and a thickness of an antenna adapted for the
bandwidth and reading distance of the RFID tag; preparing ink for
manufacturing the RFID tag; determining temperatures and distances,
respectively, for a drying zone and a curing zone, considering curing
conditions of the ink and an anticipated operation rate; determining a
substrate; determining a type of a roll-to-roll printing process, a cell
shape and a cell depth; determining process conditions; printing the
antenna; examining the printed pattern of the antenna; drying the
substrate with the printed antenna; examining the printed pattern of the
antenna; curing the substrate with the printed antenna; examining
conductivity of the cured antenna; bonding a RFID chip to the antenna;
testing final performance of the RFID tag in view of the bandwidth and
reading distance; and repeating the steps prior to printing the antenna
when any of the printed pattern, the conductivity, and the final
performance is not within respective predetermined tolerance ranges of
error.

[0020]In an aspect of the invention, designing the shape and thickness of
an antenna may be performed considering sensitivity of RFID driving
performance to work surroundings and noise under which the RFID tag is to
be used.

[0021]In an aspect of the invention, preparing ink may include determining
a type, viscosity, and metal contents of ink. Determining the substrate
may include determining the type, width, thickness of a web material to
be used as a substrate in consideration of the surface tension and
roughness of the substrate, the degree of adhesion interaction between
the substrate and the ink, and drying and curing temperatures such that
the substrate is not melted at a drying temperature and a curing
temperature.

[0022]The determination of the type of a roll-to-roll printing process may
be performed considering the type and viscosity of ink and the type of
substrate, and the determination of a cell shape and a cell depth may be
performed by considering the shape and thickness of the antenna. Also,
the determination of process conditions may include, in an aspect of the
invention, determining an operation rate, an operation tension, and a
feed roll pressure.

[0023]In another aspect of the invention, the method of manufacturing an
RFID tag using a matching logic may further include the step of
determining change of a scheduling scheme and change of register and
tension control methods.

[0024]In an aspect of the invention, the examination of the printed
pattern of the antenna may be performed by visually checking the
thickness, thickness uniformity and any spreading of the printed pattern,
using a microscope. Also, the examination of conductivity of the cured
antenna may include checking any breakage or short-circuit of the printed
pattern.

[0025]In accordance of the present invention, one of the advantages
provided by the matching logic in the present invention is the capability
of mass production of electrical devices and significant reduction of
production cost and time, which results from effective, comprehensive and
systematic designing of the roll-to-roll printing process by determining
critical process conditions and production parameters through the
matching logic.

[0026]Another advantage of the present invention is the capability of
efficiently and promptly controlling quality of the electronic devices
produced by repeatedly checking the printing errors at steps known as the
frequent sources of error and eliminating them by systematically
recalibrating the conditions and parameters of the roll-to-roll printing
process through the matching logic.

[0027]A further advantage of the present invention is to provide a method
of manufacturing a RFID tag using a roll-to-roll printing process through
the matching logic.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is part of a flowchart schematically illustrating a process
of printing an electronic device using a matching logic according to the
present invention;

[0029]FIG. 2 is part of a flowchart, continuing from the flow chart in
FIG. 1, schematically illustrating a process of printing an electronic
device through a matching logic according to the present invention; and

[0030]FIG. 3 is a flowchart schematically illustrating a process of
manufacturing an RFID (radio frequency identification) tag using a
roll-to-roll printing process using a matching logic according to the
present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031]The drawings, FIGS. 1-3, to be described herein are shown for
purposes of illustrating only certain embodiments of the present
invention, and not for any purpose of limiting the invention. Further,
the terms and words used in the present specification and claims should
not be interpreted as being limited to typical meanings or dictionary
definitions, but should be interpreted as having meanings and concepts
relevant to the technical scope of the present invention.

[0032]FIGS. 1 and 2 show, as combined, a flowchart illustrating a method,
in accordance with the present invention, of producing an electronic
device using a roll-to-roll printing process, by using matching logic.
Before utilizing the method of the present invention, the type of a
particular electronic device to be printed by a roll-to-roll process
using the method in the present invention is chosen. The electronic
device may be chosen from any electronic device that is printable, which
may include, but is not limited to, a RFID (radio frequency
identification) tag, a solar cell, a signage, or other electronic devices
compatible for production by utilizing a roll-to-roll process.

[0033]Referring now to FIG. 1, the first step of the method in the present
invention is to determine the specs of the chosen electric device to be
printed. (S10) Such specs could include target values of the conductivity
of the printed electric circuits, other electric properties or functions
specific to the selected electronic device, and their respective ranges
of tolerance of error. The specs are determined in consideration of the
current level of printing technology and its accuracy, and vary depending
on the specific type of the electronic device selected. For instance, if
the subject matter is a RFID tag, the specs to be determined in this step
may include the conductivity, the bandwidth and reading distance of the
RFID tag, and respective ranges of tolerance of error.

[0034]The next steps in the present invention are to determine, by
applying the matching logic, a variety of matching conditions that are
needed to be determined for producing the target electric device using a
roll-to-roll printing. In the matching logic, such conditions are
determined so as to be adapted for the specs of the target electronic
device that are determined in the first step (S10) and also in such a way
to be technically, chemically, and mechanically commensurate and
compatible with other relevant matching conditions determined in the
matching logic.

[0035]The types of matching under the matching logic to determine such
matching conditions may include impedance matching, chemical matching,
process matching, geometry matching, mechanical matching and time
matching (S20-S70). Specifically, the matching conditions to be
determined in each type of matching are as follows.

[0036]The matching conditions to be determined during the impedance
matching (S20) may include, in an embodiment of the present invention,
the thickness of a printed pattern (skin depth) and intervals between
neighboring lines in the printed pattern (trace design). These conditions
are determined in consideration of the specs of the target electronic
device in S10. In another embodiment of the present invention, the
conditions to be determined during the impedance matching may include the
sensitivity of the electronic device to be printed, which may be
determined in consideration of the surroundings in which the electronic
device is worked or used. For instance, if the electronic device is a
RFID tag, the sensitivity of its driving performance is determined in
view of expected work surroundings and noise level.

[0037]The matching conditions to be determined during the chemical
matching (S30) include the ink conditions and substrate conditions. The
ink conditions may include the type of ink, the composition of the ink
such as the metal content, the metal particle size, the properties of ink
such as the viscosity, which may be used to determine the degree of
mixing of ink with a solvent, the amount of ink to be transferred to a
substrate, the behavior of the ink transferred from a printing pattern on
a roll upon transfer of the ink, and whether the ink is water-soluble or
lipid-soluble.

[0038]In the process matching, the type of a particular roll-to-roll
printing process is determined (S40). Examples of a roll-to-roll printing
process for use with the present invention may include gravure printing,
flexographic printing, offset printing and hybrid printing, each of which
requires printing rolls, and ink-jet printing which does not. In
determining the particular type of the printing process, the previously
determined matching conditions, in particular, the cell width on the
printing roll determined in the impedance matching and ink viscosity
determined in the impedance matching are primarily considered.

[0039]After the type of roll-to-roll printing process is determined, the
geometry matching (S50) determines, if the determined printing process
uses printing rolls: the shape (cell shape), depth (cell depth) and width
(cell width) of a recessed cell in the printing rolls. These matching
conditions are closely dependent upon the conditions determined in the
impedance matching such as the shape, thickness (skin depth), and width
of the printed pattern as well as the intervals between neighboring lines
in the printed pattern (trace design), and also correlated with the
amount of ink to be transferred. The shell shape in the printing rolls
may be a quadrangular shape, a pyramidal shape or a tri-helical shape.
The geometry matching may further determine the coating property of a
printing roll, for instance, the kind of a coating material such as
nickel, chromium, etc. If the target electronic device is a RFID tag, the
size and position of the RFID chip to be bonded after the antenna is
printed must be also considered in determining the above-mentioned
conditions for a recessed cell on printing rolls.

[0040]After the particular type of roll-to-roll printing process is
determined, the various specs of the roll-to-roll printing process are
determined during the mechanical matching (S60) in consideration of the
matching conditions determined in the previous steps of the process in
the present invention, S20-S50. The matching conditions to be determined
during this matching may include, in an embodiment of the present
invention: operation tension, which is the tension applied to the subject
matter printed upon the substrate while in transit; nip force, which is
the pressure between an impression or nip roll and a printing or feed
roll upon printing; the pressure of a riding roll for preventing inflow
of air upon winding; operation rate, which is transport velocity of the
substrate, and is correlated with the rate and amount of transfer of ink;
and drying and curing conditions.

[0041]The drying conditions may include the duration, temperature and
distance of a drying zone, and means for drying such as hot air or other
kind of gas. Similarly, the curing conditions may include the duration,
temperature and distance of a curing zone, and the means for curing. For
curing, which is to solidify and protect the printed pattern that is
transferred onto a substrate in a liquid or gel state, commonly used
curing materials are infrared light, ultra-violet light or electron
beams. In determining the drying and curing conditions, the operation
rate is considered. In determining the curing conditions, the curing
condition of ink is also considered.

[0042]In an embodiment of the present invention, the mechanical matching
may further determine additional specs of the particular roll-to-roll
printing process that may include: the tension of each span between
consecutive printing rolls before and after printing; the ratio of width
to the length (the interval between rolls) of the substrate; taper
tension applied to the printed subject matte at the stage of winding it
around a winding roll; the precision of a register control specific to
the chosen roll-to-roll printing process; and a cooling process.

[0043]The substrate conditions, part of the matching conditions determined
during the chemical matching (S30), may include the type, width and
thickness of a web material to be used as the substrate. In such
determination, the ink conditions that have been previously determined
are considered such that the substrate may be chemically adapted for and
compatible with the determined type of ink utilized in the process.
Particularly, the substrate properties such as the surface tension and
roughness and the degree of adhesion interaction between the substrate
and the ink to be transferred thereon are considered. Also, the drying
and curing temperatures, which are determined in the mechanical matching
(S60), are considered such that the substrate is not melted at the drying
and curing temperatures.

[0044]The matching conditions to be determined during the time matching
(S70) may include, in an embodiment of the present invention: change of
any scheduling scheme in a real time operating system (OS) such as RM
(rate monotonic), EDF (earliest deadline first), LDF (latest deadline
first) or etc.; change of any register or tension control method such as
PID (proportional integral derivative) control, feed-forward control,
MIMO (multi input multi output) control; and change of input/output
synchronization.

[0045]Now referring to FIG. 2, after the subject matter, an electric
circuit, is printed with the ink through the roll-to-roll process, the
state of printing of the electric circuit is visually examined by,
preferably, a microscope (S80). In other embodiments, however, the
examination may be performed by utilizing sensors. Specifically, the line
thickness, thickness uniformity, and any spreading of printed lines may
be checked. If the printed state is not within the tolerance range of
error predetermined in S10, as indicated by the `NO` in S80 in FIG. 2,
the procedure returns to the prior steps of the present invention, S20
through S70, where matching conditions are re-determined and readjusted.
But, if the printed state is good, as indicated by the `YES` in S80 in
FIG. 2, the procedure proceeds to the step of drying the printed subject
matter (S90), in which the printed subject matter are dried under the
drying conditions and means previously determined in S60.

[0046]In an embodiment of the present invention, the printed subject
matter may be re-examined (S100), for example, visually by a microscope
or by using sensors, after drying the subject matter for any error in the
printed lines that may have occurred during the drying step due to, for
example, hot air or gas. Again, the line thickness, thickness uniformity,
and any spreading of printed lines may be checked. If an error in the
printed lines is greater than the predetermined tolerance range of error,
as indicated by the `NO` in S100 in FIG. 2, the procedure returns to the
prior steps, S20 through S90, where matching conditions, especially the
drying conditions, are re-determined and readjusted. But, if the printed
state is good, as indicated by the `YES` in S100 in FIG. 2, the procedure
proceeds to the next step of curing the printed subject matter (S110).

[0047]Next, the dried subject matter is cured (S110) under the curing
conditions by using the curing materials previously determined in S60.
During curing, the printed ink is metalized and metal particles are
melted and interconnected.

[0048]After curing the subject matter, conductivity of the cured subject
matter, the electric circuit, is examined (S120) to spot any physical
breakage of printed lines or short-circuit of the printed lines. If the
value of conductivity is not within the predetermined tolerance error
range from its target value, as indicated by the `NO` in S120 in FIG. 2,
which may be one of the previously determined specs of the electronic
device in S10, the procedure again returns to the prior steps, S20
through S110. But, if the value of conductivity falls within the
predetermined range of error tolerance, as indicated by the `YES` in S120
in FIG. 2, the procedure proceeds to the next step (S130), where
performance of a final product is tested. Here, whether the electric
properties or functions specific to the printed electronic device measure
up to the target values preset in S10 in determining the specs of the
electronic device are tested. For example, if the target electronic
device is a RFID tag, what is tested in this step may be the receiving
distance and reading rate of the RFID tag.

[0049]Again, if the performance test result of the final product is not
satisfactory, that is, the tested values of the electric properties or
functions specific to the printed electronic device are greater than the
respective ranges of error tolerance predetermined in S10 as indicated by
the `NO` in S130 in FIG. 2, the procedure once again returns to the prior
steps S20 through S120. If the final product performance is satisfactory
enough, as indicated by the `YES` in S130 in FIG. 2, the production of an
electronic device via a roll-to-roll printing process, by using a
matching logic in the present invention, is completed.

[0050]FIG. 3 is a flowchart showing a process of producing a RFID (radio
frequency identification) tag using a roll-to-roll printing process using
matching logic according to one embodiment of the present invention.

[0051]First, target values of the bandwidth and reading distance of the
RFID tag to be manufactured, and their respective ranges of tolerance of
error are determined (S210). For example, in one embodiment, the
bandwidth of the RFID tag may be 900 MHz and the reading distance may be
six meters or more.

[0052]Next, a RFID antenna is designed using an impedance matching (S220)
such that it may be adapted for the bandwidth and the reading distance of
the RFID tag determined in the previous step. In this matching, for
example, the shape and thickness of the antenna are determined. In such
determination, the sensitivity of the driving performance of the RFID tag
to work surroundings and noise under which the RFID tag is to be used may
be considered.

[0053]In the next stage, as part of the chemical matching, the type of ink
to be used for manufacturing the RFID tag is determined (S230), together
with its properties such as the metal contents in the ink and the
viscosity of the ink. In one embodiment of the present invention, the ink
may contain silver nano-particles.

[0054]Next, the curing and drying conditions, part of the mechanical
matching conditions, are determined in (S240). The curing conditions may
include the curing temperature and the curing distance, which the subject
matter will travel during a curing procedure in the curing zone.
Similarly, the drying conditions may include the drying temperature and
the drying distance. In determining those conditions, the curing
conditions of the ink and the anticipated operation rate may be
considered. In one embodiment of the present invention, the curing
temperature is 150 degree Celsius, the curing time is 180 seconds, the
operation rate is 20 meters/min, and the curing distance is 60 meters.

[0055]In the next stage, another part of the chemical matching, the type
of a substrate is determined (S250). The type of the substrate is chosen
such that the substrate will not melt at the previously determined drying
and curing temperatures during the drying and curing procedures after the
antenna is printed on the substrate. Also, it should be taken account
that the substrate may be subjected to a surface roughness treatment or a
surface coating treatment depending on the adhesion interaction between
the substrate and the previously selected ink. In one embodiment of the
present invention, the substrate may be a thermosetting PET (polyethylene
terephthalate).

[0056]Next, the type of a roll-to-roll printing process is determined, in
process matching, so as to be adapted for the type and viscosity of ink
and substrate selected (S260). In one embodiment of the present invention
that uses ink containing silver nano-particles and thermosetting PET as
the substrate, a gravure printing is chosen for printing the RFID tag.
After then, the cell shape and depth on printing rolls is determined
using geometry matching by considering the shape and thickness of the
antenna to be printed, which have been previously determined during
impedance matching. In the embodiment of the present invention that uses
a gravure printing, the cell has a square shape with the cell depth of 39
micrometers.

[0057]After the type of a roll-to-roll printing process is determined, the
specs for the roll-to-roll printing, or the process conditions, are
determined using mechanical matching (S270). The process conditions may
include an operation tension, an operation rate, and a feed roll pressure
or nip force. In one embodiment of the present invention, the operation
tension is chosen to be 60 Newtons, the operation rate is 20 meters/min,
and the feed roll pressure is 20 Newtons. In one embodiment, the process
conditions may further include pressure of a riding roll for preventing
inflow of air upon winding, tension of each span between consecutive
printing rolls, width-to-length ratio of the substrate, taper tension,
precision of a register control, and a cooling process.

[0058]After the printing is performed by the particular roll-to-roll
printing process and process conditions determined in steps (S260) and
(S270), the quality of the printed pattern is visually examined using a
microscope (S280). In particular, the line thickness, uniformity in
thickness, and any spreading of printed lines may be checked. If the
printing quality is poor, that is, if the error measured goes beyond the
predetermined range of tolerance of error, the procedure returns to the
prior steps, (S230) through (S270), where the matching conditions
previously determined are re-determined and readjusted.

[0059]Next, the subject matter having the printed pattern is dried under
the previously determined drying conditions, and the dried subject matter
is checked by using a microscope (S290) for any error in the printed
lines that might have been generated due to hot air used for the drying.
In particular, the line thickness, thickness uniformity, and any
spreading of printed lines may be checked again. If the printing quality
is beyond the predetermined tolerance of error range, the procedure
returns to the prior steps and repeats the steps of (S230) through
(S280).

[0060]Next, the dried subject matter is cured (S300) at the curing
temperature for the curing time determined at the prior step of (S240).

[0061]After the curing of the subject matter having the printed pattern,
the electrical conductivity of the cured printed pattern is tested and
any physical breakage or short circuit thereof is examined (S310). If the
value of conductivity is not within the predetermined error tolerance
range for conductivity, the procedure again returns to the prior steps,
(S230) through (S300).

[0062]Next, a RFID chip is bonded to the printed antenna (S320). Lastly,
the bandwidth and reading distance are checked as the indicator of the
degree of performance of the final product, the RFID tag (S330). If the
values of the bandwidth and reading distance are not within the
predetermined respective error tolerance ranges, the procedure again
returns to the prior steps, (S230) through (S320).

[0063]While particular forms of the inventions have been illustrated and
described, it will be apparent to those skilled in the art that various
modifications, additions and substitutions can be made without departing
from the inventive concept. References to use of the invention with a
specific materials or procedures in describing and illustrating the
invention herein are by way of example only, and the described
embodiments are to be considered in all respects only as illustrative and
not restrictive. The present invention may be embodied in other specific
forms without departing from its spirit or essential characteristics.
Accordingly, it should be understood that the scope of the invention is
defined by the accompanying claims only.